FLIGHT TEST: Bombardier 415 - The superscooper

Not every child grows up wanting to be a fireman, but for me it was a close second after being a pilot. Perhaps too late for me, I seem to have stumbled upon the perfect vocation for someone with my workplace dreams and desires: piloting a Bombardier 415, the latest and most capable amphibian the Canadian mainframer has produced.

The 415 traces its roots to theCanadair CL-215, which first flew in 1967, and is the third iteration in this venerable line of amphibians. One hundred and twenty-five of the piston-powered CL-215s were produced, with the final aircraft delivered in May 1990. While the piston-powered aircraft had proven to be quite reliable, the benefits of turbine power were not lost on Canadair, which developed a turbine conversion kit for the CL-215. The CL-215T has Pratt & Whitney Canada 123AF turbines in place of the 215's 2,100hp (1,566kW) R-2800 radial engines. To date 17 aircraft have been converted, with the turbine conversion kit offered alongside the new- build 415.

Before I saw the 415 in the flesh, Bombardier provided me with a brief tour of its production facility in Montreal, giving valuable insight into the unique nature of the amphibian. It is made the old-fashioned way - aluminium is cut, bent and fashioned into the final product. Critical parts of the aircraft are made with treated aluminium, allowing it to operate in fresh and salt water. Pictures do not do justice to the aircraft's size: its flaps match Cessna Caravan wings; the 100m2 (1,076ft2) wing has a span of 28.6m (97ft), nearly as long as a Boeing 737's. The sizable highly cambered wing gives the 415 great short take-off and landing (STOL) performance and a remarkably slow stall speed of 68kt (126km/h).

With the spring thaw in full swing, Flight International was offered the opportunity to take the Superscooper for a dip in Sault Ste Marie, Ontario, Canada. The Ontario Ministry of Natural Resources had graciously offered one of its nine 415s for the demonstration flight. Garry Stewart, chief fixed-wing pilot, acted as the pilot in command for what was to be my first flight in a flying boat.

In the warmth of a heated hangar, Stewart pointed out several of the aircraft's unique features. It rests on tricycle landing gear when in the land mode. The nose gear retracts backward into a well on the hull's centreline. The nose gear doors meet at the hull's "V", and contrary to my expectations, do not seal the compartment. Water will inevitably get into the wheel well, and two drains at the aft end of the well evacuate water once airborne.

Two water tanks, each holding 3,655 litres (810USgal) of water, are located roughly at the aircraft's centre of gravity. The tanks are located predominately below the floor in the hull, with each side having a header tank that rises into the fuselage compartment. Forward of each water header tank is a 340.5 litre (681 litre total) foam tank, enough foam for 20 drops. Typically, the foam tanks are filled with a short-term retardant that "gels" the water, allowing it to hang up in the forest canopy and delaying run-off when it reaches the ground. The water tanks can be filled on the ground with ground fill adapters on each side of the fuselage.

Maximum take-off weight from the ground is 19,890kg (43,800lb), while maximum weight after scooping - the primary way to load water - is 21,364kg. Water is "scooped" through two hydraulically actuated 7.6 x 12.7cm (3 x 5in) probes that are much too small to ingest a scuba diver, contrary to some popular urban legends. The probes are just aft of the hull's step. Forward of the step are the four hydraulically operated drop doors, two for each tank.

The more powerful engines and larger composite propellers of the 415, compared with the CL-215T, necessitated several aerodynamic changes. To maintain engine-out controllability, with the original 215's rudder moment arm, the 415's engines are mounted closer to the fuselage. Large winglets/canted wing endplates, unique to the 415, also improve directional stability. Finally, an inverted fixed leading edge slat is mounted forward of the right-hand horizontal stabiliser. Moving the engines inboard had the unintended consequence of degrading longitudinal stability, rectified by the asymmetric slat.

WATER SYSTEM CHECKS

Outside the hangar, pre-flight inspection of 415 (registration number C-GOGF) was straightforward and had the overall feel of inspecting a very large high-wing Cessna. Entry into the seaplane is via a boarding ladder into the forward left-hand entry door. The cabin is quite large, with the header and foam tanks located in the forward half of the cabin.

The flightdeck is relatively wide, with a deep access way running between the captain and co-pilot seats. The access way led to the hatch on the bow of the seaplane, allowing mooring from inside the aircraft. Throttles are placed on the centre console, which span across the access way. Aircraft systems are controlled by logically arranged sub-panels on the cockpit overhead panel. The forward instrument panel is also well arranged around the primary flight instruments.

The EICAS system consists of three 5 x 6in electronic flight instrument screens in the centre of the panel. Unique to the 415 - because it is a water bomber - is the water status panel. This allows the pilots to control the water bombing system, from scoop to drop. With empty aircraft weight entered and real time fuel state, the system graphically displays how much water can be scooped. This handy system minimises crew workload during the high-intensity scooping operation.

Water drop pattern is also controlled by this panel, allowing various patterns from the salvo of all tanks (most common drop method), to timed interval drops of individual tanks.

FIREFIGHTING ADVANTAGE

Along with seaplanes, land-based aircraft and helicopters are also used to fight fires and each type has its strengths. Large land-based bombers can carry large loads, but are tied to runways that may be far from the fire. Helicopters can use buckets to scoop water from nearby water sources, but they typically have a limited payload capability and slow transit speeds.

The 415 and its brethren combine the large payload capability of land-based fire bombers with the rapid replenishment capability of bucket-equipped helicopters. For a typical firefighting mission, the 415 takes off from land and cruises at low altitude to a point near the fire to scoop water for the initial attack. A 2,722kg fuel load, typical for firefighting, gives a mission endurance of about 4.5h.

According to Bombardier, with water 6-15km (3.2-8nm) away from a fire, the 415 can complete from seven to 12 drops in an hour. The aircraft can be productive, capable of emptying up to 125,000 litres of water an hour on a fire. These figures compare favourably with actual utilisation data from the Canadian 415 fleet, where each aircraft flew about 200h, including training, ferry and actual firefighting missions. For each flight hour an average of 6.9 water drops were accomplished.

My demonstration flight mirrored a typical firefighting mission, except that our time on the "fire" was only about 30min. Roy Vinall, a line 415 captain, read the checklist while Stewart and I performed pre-start checks. The uneventful engine start was followed by checks of the hydraulically boosted flight controls as well as the water drop system, ensuring the drop doors opened and closed as commanded.

The flat-rated PWC123AF engines provide 2,380shp of continuous power each at conditions up to ISA +20°C (68°F), but do not have FADECs, in part because in an emergency situation pilots like to have maximum engine power available, even if it means "over temping" the engines. To prevent exceedances in normal operations, thrust limit screws are placed on the throttle quadrant. Using a panel-mounted lookup table, throttle travel is restricted by a soft stop, preventing routine exceedances, but allowing for maximum thrust in an emergency.

Stewart taxied the 415 to Sault Ste Marie's Runway 30 for take-off. Flaps were set to 15° before lining up into a stiff 26kt headwind. With 2,722kg of fuel the 415 leapt off the runway after a ground run of less than 600m. Bombardier publishes a land take-off distance of 838m for a 19,890kg aircraft. Flaps were retracted at an indicated airspeed of 110kt during the climb out to a cruise altitude of 2,000ft. Cruise power of 87% torque and 900 RPM gave a true airspeed of about 190kt, with a total fuel flow of 712kg/h (1,570lb/h).

I was pleased to find the control forces were easily trimmed out and aircraft stable at cruise speed, given that there is no autopilot control. During the cruise I did some 30° angle-of-bank turns. The 415 is not a feet-on-the-floor aircraft, and I found the hydraulically boosted ailerons and rudder to be well harmonised during the turns. Control forces in the boosted pitch axis were relatively lighter than those in roll and yaw, and I found the aircraft somewhat pitch sensitive at cruise speed.

About 20km east of Sault Ste Marie is a 1km-wide bulge in the river that separates Canada and the USA. The Canadians call this 3km long body of water Little Lake George, perhaps in homage to the 18th century English king. The Americans, who perhaps have no such feelings for the king they fought in the Revolutionary War, have no name for that particular part of the river.

Approaching from the west we surveyed the lake from 500ft above the ground. Wind streaks on the surface indicated a 20kt wind out of the west with wave heights of 0.4m. Checklist usage and procedural discipline are extremely important during water and firefighting operations, with Vinall again running the appropriate checklist. Alighting in the water with the landing gear down is a recipe for disaster and particular attention was paid to the aural warning selector switch, which was positioned to "sea" for our impending water landing.

Stewart demonstrated a water landing and subsequent take-off. A steep final approach angle was used, the 10° nose low attitude resulting in a descent rate of 2,000ft/min at and indicated airspeed of 110kt with flaps set to 40°. Touchdown was at idle power in a slightly nose-up attitude, with continued aft yoke pressure held until the aircraft slowed to a stop.

At our current weight, Stewart estimated the 415 had a draft of less than 1m, with 1.8m water depth required for operations. The flaps were set to 10° and power advanced for the water take-off. At about 55kt, the 415 lifted on the step, with lift-off at 80kt. The flaps were set to 15° for a scoop and drop operation, the bread and butter of the 415's mission.

SCOOP AND DROP

One great advantage the 415 has as a STOL aircraft is its ability to operate at slow speeds. These slow speeds allow it to scoop out of small bodies of water, a full load requiring a water run of only 410m. With 15m obstacles surrounding a body of water, a total distance of only 1,341m is needed to scoop a full load.

Rapid thrust response is critical in firefighting operations, and the 415's turboprop engines are crucial to its success. The radial engine CL-215 boasted nearly instantaneous throttle response from 0 to full power. Typical commercial jet engines have a long spool-up time, with idle to full power taking up to 6s. The PW123s on the 415 can reach full power from idle in 1s, a necessary capability when flying a heavily laden aircraft low and slow over a forest fire.

The approach to Little Lake George was into the wind and much like the final approach to a landing. Vinall again ran the checklist and guided me through the water panel set up for the scoop. Two pop-up "spigots" in the nose access way indicated the nose gear doors were closed. The two hydraulically actuated scoops were extended, and water on-load amount, 5,897kg, confirmed by reference to the water status panel.

Stewart flew the first scoop run, with flaps again set to 15°. Once on the water a power setting of 80% torque kept an indicated airspeed of 75kt as water filled the tanks. As the water load approached 4,763kg, I closed the scoops, with the remainder of the desired load filling as the scoops closed.

Scoop complete, the power was advanced to about 90%. The flying boat lifted off the water at 85kt. Actual fire drops are conducted at 100-150ft above the ground. For the demonstration drop, Stewart flew at 200ft radar altitude. On a downwind heading over Lake George the full load was salvoed into the water.

Next it was my turn to scoop and drop. Stewart and Vinall ran the checklists to ensure we were ready to scoop. Approach to the scooping zone was again at flaps 15° at 110kt with a descent rate of nearly 2,000ft/min. On short final I centred the elevator trim, with a good amount of forward yoke pressure needed to maintain the desired approach path. At about 20ft radar altitude I retarded the throttles to idle and started the flare manoeuvre.

Splashdown was in a nearly level attitude. Once on the water the yoke was held steady in the position it was at touchdown, with little or no yoke force needed to maintain the desired attitude. I advanced the throttles to about 80% torque, and the 415 skimmed across the water at 75kt.

Stewart retracted the scoops as the water approached the fill lines on the water status panel. With the scoops retracted I advanced the power levers and the 415, already on the step, lifted smartly off the surface.

In the US military, I had the opportunity to practise dropping bombs from a number of different aircraft, but this was to be my first time dropping water. The approach for the drop was at 500ft radar altitude, with the flaps set to 15° at 110kt. While there was no fire to extinguish, I did pick a desired aim-point I wanted to drench on the lake's surface. Just before my target I pushed the release button on the outboard horn of the yoke. In less than 1s the entire load was dropped.

I had half-expected the sudden decrease in weight to cause the 415 to pitch up wildly, requiring near Chuck Yeager-like reflexes to save the day. In reality the aircraft proved to be quite stable and predictable during the drop. As the tanks emptied, less than 0.2m of forward yoke travel at moderate pace was needed to maintain a level attitude.

EMERGENCY DUMP

Time allowed for another two scoop and drop runs, and with each run I was better able to relish the exhilaration of racing across the water at 75kt. After the last scoop run while climbing through 100ft radar altitude, Stewart pulled the right engine to idle, to simulate an engine failure at our high gross weight condition.

While less than one-half left rudder was needed to maintain heading, the rate of climb was decreasing rapidly. At Stewart's direction, I pulled the manual emergency dump lever, located to the right of the throttle quadrant. This system bypasses the water control panel, and the now 5,897kg lighter 415 re-established a rapid climb rate.

Our return to Sault Ste Marie was on both engines to a full stop landing with the flaps set to 25°. Vinall completed the appropriate checklists en route, and of note ensured the aural warning selector switch had been placed to "land".

During the landing roll-out wheel brakes alone were used to slow the seaplane. Stewart taxied back to the Ministry of Natural Resources ramp, using reverse thrust on both propellers to back into its parking spot.

MULTIPURPOSE SEAPLANE

During my brief evaluation flight in the Superscooper I was surprised by how easy the 415 was to fly. While my experience in seaplanes is limited, I found it easy to operate on the water and it handled waves better than the Twin Otter I had flown earlier this year.

Its rapid reload capability and ability to scoop water from water bodies as short as 410m gives it an impressive firefighting capability. This capability comes at a price, $28.5 million for a new build aircraft.

While certainly not the most inexpensive firefighting aircraft, a total of 71 of these highly capable rugged firefighting seaplanes have been ordered. As a natural extension of the 415 range, Bombardier has developed the 415MP. The MP is a multipurpose version for law enforcement, search and rescue to utility transport missions. To date, four MPs have been ordered, bringing the total for the 415 family to 75.

With the 415 seemingly in a niche of its own, it is not surprising that it has been a success with governments the world over.